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I just set up raid 5 on linux using three HDDs as per a guide. It all went fine until when I rebooted I got the following text:

Does this mean one of my HDDs has failed? How do I check if any of them are failing? I tried using smartctl and didn't see any issues. Or is it nothing to do with failure and something else altogether? I would like to get the raid 5 working again but I'm not sure where to go from here.

I'm using ubuntu 12.10 and the three raid disks each have a gpt partition with a single full size partition of filesystem type ext4. Note I only got an error on reboot not while I was creating the raid array which went fine.

I intended to use sda, sdb and sdc for the raid 5 array.


CREATE owner=root group=disk mode=0660 auto=yes
HOMEHOST <system>
ARRAY /dev/md0 metadata=1.2 spares=1 name=bluelady:0 UUID=e0839614:9f79606f:75191039:19d511db


Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md127 : active (auto-read-only) raid5 sda[0] sdc[3] sdb[1]
      7813774336 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
unused devices: <none>


/dev/md0                    /data       auto    defaults,user,owner 0   2


share|improve this question
Your system seems to recorgnise SDB and SDC as part of the array. That is 2 out 3 of, so yes, one of the drives has failed or is otherwise not correctly recognised as part of the array. Which drives did you expect to use sda,b, and c? What is in /etc/mdadm? – Hennes Nov 2 '12 at 17:07
@Hennes I've answered your questions as updates to my original post. Please see there. Thanks. – junkie Nov 2 '12 at 17:20
you have a spares=1 in mdadm.conf. As I understand it that is an as yet unused spare disk, leaving you two drives for the RAID5 array. That seems wrong. Hopefully someone with more mdadm experience can answer this. – Hennes Nov 2 '12 at 17:35
@Hennes The command I used to create the array was: mdadm --create --verbose /dev/md0 --raid-devices=3 --level=5 /dev/sda /dev/sdb /dev/sdc. I didn't specify any spares explicitly. – junkie Nov 2 '12 at 17:48
Could you 1) Check the output of mdadm --detail --scan. Does it list any spares. If it does not show any spares, how does the system boot if you temporarily remove that keyword from mdadm.conf (no full reboot needed, try single user mode umount, remove keyword, mount.) – Hennes Nov 2 '12 at 17:51

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